Metal ion-doped lithium iron phosphate material, preparation method and application thereof

Abstract

The disclosure provides a metal ion doped lithium iron phosphate material and a preparation method and application thereof, and relates to the technical field of lithium batteries. The metal ion doped lithium iron phosphate material comprises flaky lithium iron phosphate and metal ions doped on the flaky lithium iron phosphate, and the flaky lithium iron phosphate has a porous structure. The method comprises the following steps: using an organic metal compound as a deposition raw material to deposit a carbon layer and metal oxide particles on the surface of a porous Fe2O3 flaky precursor to obtain a composite material; mixing the composite material, a lithium source and a phosphorus source according to a stoichiometric ratio, and then drying and sintering to obtain an M-LiFePO4 material. The M-LiFePO4 prepared by the disclosure has good uniformity and is not prone to agglomeration, inherits the two-dimensional flaky morphology of the precursor material and has a porous structure, has good rapid charging and discharging capacity, and improves the rate performance of the lithium iron phosphate material through doping of metal ions.

Description

Technical Field

[0001] This disclosure relates to the field of lithium battery technology, and more specifically, to a metal ion-doped lithium iron phosphate material, its preparation method, and its application. Background Technology

[0002] With the depletion of fossil fuels and the urgent need for renewable energy, efficient electrochemical storage systems have been vigorously developed in recent years. Lithium-ion batteries, with their high energy density and long cycle life, have been widely used in energy storage devices such as large-scale smart grids and portable electronic devices. Lithium iron phosphate (LiFePO4) is a novel cathode material for lithium-ion batteries. Due to its excellent characteristics such as high capacity, stable operating voltage, good cycle performance, and good safety, it has become the preferred cathode material for power and energy storage batteries. However, due to its inherent structural limitations, lithium iron phosphate materials suffer from low electronic / ionic conductivity, low lithium-ion diffusion rate, and low tap density, which leads to poor rate performance and limits its further practical applications. Currently, methods such as material nanosizing, ion doping, morphology control, and carbon layer coating are used to modify lithium iron phosphate to improve the capacity retention and specific capacity of lithium-ion batteries. Doping with metal ions can create lattice defects in lithium iron phosphate, widening the ion diffusion channels and reducing the band gap to improve the material's electronic conductivity. Nanoparticle size can increase the specific surface area of ​​the material and effectively shorten the lithium-ion diffusion path, thus improving its diffusion rate. Special morphological structures can increase the contact between the material and the electrolyte, providing more electrochemical active sites, which is beneficial for the rapid insertion and extraction of lithium ions. Carbon coating not only improves the conductivity of the material but also restricts grain growth and inhibits particle aggregation. Although modified lithium iron phosphate materials have been prepared using these methods, most suffer from drawbacks such as complex processes, high energy consumption, poor particle uniformity and density, low product purity, and limited improvement in rate performance, making it difficult to meet industrial requirements. Therefore, addressing the shortcomings of existing technologies and developing a simple and convenient method to prepare novel lithium iron phosphate cathode materials with excellent performance parameters is of great significance for improving the overall electrochemical performance of lithium batteries and promoting their large-scale market application.

[0003] In view of this, this disclosure is hereby made. Summary of the Invention

[0004] The purpose of this disclosure is to provide a metal ion-doped lithium iron phosphate material, its preparation method, and its application.

[0005] This disclosure is implemented as follows:

[0006] In a first aspect, this disclosure provides a metal ion-doped lithium iron phosphate material, comprising: sheet-like lithium iron phosphate and metal ions loaded onto the sheet-like lithium iron phosphate, wherein the sheet-like lithium iron phosphate has a porous structure.

[0007] In an optional embodiment, the molar ratio of iron to metal ions in the sheet-like lithium iron phosphate is 1:(0.03~0.1).

[0008] In an optional embodiment, the thickness of the sheet-like lithium iron phosphate is 30nm-60nm.

[0009] In an optional embodiment, the specific surface area of ​​the sheet-like lithium iron phosphate is 12.5 m². 2 / g-14.7m 2 / g.

[0010] Secondly, this disclosure provides a method for preparing a metal ion-doped lithium iron phosphate material, comprising:

[0011] Using organometallic compounds as deposition materials, a carbon layer and metal oxide particles were deposited on the surface of a porous Fe2O3 sheet-like precursor to obtain an Fe2O3-C / MO composite material, wherein M is a divalent transition metal ion Co. 2+ Ni 2+ Mn 2+ One of them;

[0012] The Fe2O3-C / MO composite material, lithium source, and phosphorus source were mixed in stoichiometric ratio, and then dried and sintered to obtain M-LiFePO4 material.

[0013] In an optional embodiment, the organometallic compound includes at least one of bis(cyclopentadiene)cobalt, cyclododecanetriene nickel, and cyclopentadiene tricarbonylmanganese.

[0014] In an optional embodiment, the molar ratio of iron to the organometallic compound in the porous Fe2O3 sheet precursor is 1:(0.03 to 0.1).

[0015] In an optional embodiment, the deposition includes chemical vapor deposition.

[0016] In an optional embodiment, the chemical vapor deposition reaction temperature is 450°C to 550°C, and the reaction time is 1 hour to 2 hours.

[0017] In an optional embodiment, the chemical vapor deposition is performed under a protective atmosphere.

[0018] In an optional embodiment, the method for preparing the porous Fe2O3 sheet-like precursor includes: preparing ferric hydroxide carbonate by heating and reflux reaction of a mixture of ferric salt, urea and water; and obtaining the ferric hydroxide carbonate by calcination.

[0019] In an optional embodiment, the molar ratio of the ferric salt to the urea is 1:(10-15).

[0020] In an optional embodiment, the temperature of the heating reflux reaction is 90℃~110℃, the reflux time is 12h~16h, and the mixture is allowed to stand at 85℃~95℃ for 5h~8h. After the reaction is completed, the ferric hydroxide carbonate is collected by centrifugation, washed and dried.

[0021] In an optional embodiment, the washing and drying process includes washing several times with deionized water, then washing several times with anhydrous ethanol, and then drying in a vacuum oven at 70°C to 90°C.

[0022] In an optional embodiment, the calcination includes placing the ferric hydroxide carbonate in a muffle furnace, heating it to 500°C to 600°C, and calcining it in an air atmosphere for 1 to 2 hours to pyrolyze and release CO2 and H2O from the products.

[0023] In an optional embodiment, the heating rate in the muffle furnace is 3-10°C / min.

[0024] In an optional embodiment, the ferric salt is at least one of ferric nitrate, ferric chloride, and ferric sulfate.

[0025] In an optional embodiment, the molar ratio of the Fe2O3-C / MO composite material, the lithium source, and the phosphorus source is 1:(0.98~1.03):1.

[0026] In an optional embodiment, the mixing includes dispersing the Fe2O3-C / MO composite material, the lithium source, and the phosphorus source in anhydrous ethanol, and ball milling them for 2 to 5 hours, wherein the ball milling speed is 2000 rpm to 4000 rpm.

[0027] In an optional embodiment, the process further includes pre-firing before sintering, wherein the pre-firing temperature is 400–550°C and the reaction time is 2–5 h.

[0028] In an optional embodiment, the sintering temperature is 650–750°C and the reaction time is 6–10 h.

[0029] In an optional embodiment, the lithium source includes at least one of lithium carbonate, lithium hydroxide, and lithium acetate.

[0030] In an optional embodiment, the phosphorus source includes at least one of ammonium dihydrogen phosphate, ammonium hydrogen phosphate, and sodium hydrogen phosphate.

[0031] Thirdly, this disclosure provides the application of metal ion-doped lithium iron phosphate materials prepared by the preparation method of metal ion-doped lithium iron phosphate materials as described in the foregoing embodiments, or the preparation method of metal ion-doped lithium iron phosphate materials as described in the foregoing embodiments, as positive electrode materials in the preparation of lithium-ion batteries.

[0032] Fourthly, this disclosure provides a lithium-ion battery comprising a metal-ion-doped lithium iron phosphate material as described in the foregoing embodiments or a metal-ion-doped lithium iron phosphate material prepared by the preparation method of the metal-ion-doped lithium iron phosphate material as described in the foregoing embodiments.

[0033] Fifthly, this disclosure provides the application of lithium-ion batteries as described in the foregoing embodiments in the fabrication of smart grids or portable electronic devices.

[0034] This disclosure has the following beneficial effects:

[0035] The metal-doped lithium iron phosphate material disclosed herein possesses a two-dimensional sheet-like porous morphology and is doped with metal ions. Compared to irregular bulk lithium iron phosphate materials, this two-dimensional structure exhibits a larger specific surface area and abundant electrochemical reactive sites, which facilitates sufficient contact between the electrode and the electrolyte and accelerates the lithium-ion insertion / extraction rate. Furthermore, the presence of the porous structure provides ion channels for the diffusion of electrolyte ions in the vertical direction of the two-dimensional nanosheets, significantly reducing charge transport resistance and shortening the transport path and diffusion time of lithium ions and electrons. This is beneficial for improving the fast charge / discharge capability of the cathode material under high specific current. The metal ions doped on the lithium iron phosphate material can induce internal lattice defects, which is beneficial for improving the rate performance of the lithium iron phosphate material. Furthermore, the method for preparing metal-doped lithium iron phosphate materials disclosed herein uses Fe2O3 sheets as a precursor material and organometallic compounds as both a carbon source and a source of doped metal ions. The resulting metal-doped lithium iron phosphate material inherits the two-dimensional porous structure of the precursor material, and both the carbon source and the metal ion source can improve the electronic conductivity of the material. Moreover, the metal ion source introduced through the organometallic compound not only introduces internal lattice defects into lithium iron phosphate, reducing the obstacles encountered by lithium ions during insertion and extraction in the layered crystal structure, but also facilitates the stable diffusion of lithium ions into the material's lattice, thereby greatly improving the rate performance of the lithium iron phosphate material. The lithium iron phosphate sheets synthesized in this disclosure exhibit good uniformity and are not prone to agglomeration; the process is simple, easy to operate, and has low energy consumption, showing promising prospects for industrial application. Attached Figure Description

[0036] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this disclosure and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 This is a flowchart illustrating the preparation method of the metal ion-doped lithium iron phosphate material provided in this disclosure.

[0038] Figure 2 This is a scanning electron microscope image of the metal ion-doped lithium iron phosphate material provided in Embodiment 1 of this disclosure;

[0039] Figure 3 The image shows the XRD pattern of the metal ion-doped lithium iron phosphate material provided in Embodiment 1 of this disclosure. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions in the embodiments of this disclosure will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0041] This disclosure provides a metal ion-doped lithium iron phosphate material, comprising: sheet-like lithium iron phosphate and metal ions loaded onto the sheet-like lithium iron phosphate, wherein the sheet-like lithium iron phosphate has a porous structure. The molar ratio of iron to metal ions in the sheet-like lithium iron phosphate is 1:(0.03–0.1). The thickness of the sheet-like lithium iron phosphate is 30 nm–60 nm. The specific surface area of ​​the sheet-like lithium iron phosphate is 12.5 m². 2 / g-14.7m 2 / g.

[0042] This disclosure provides a method for preparing metal ion-doped lithium iron phosphate materials, which includes the following steps:

[0043] Using organometallic compounds as deposition materials, a carbon layer and metal oxide particles were deposited on the surface of a porous Fe2O3 sheet-like precursor to obtain an Fe2O3-C / MO composite material, where M is a divalent transition metal ion Co. 2+ Ni 2+ Mn 2+One method involves mixing Fe2O3-C / MO composite material, a lithium source, and a phosphorus source in a stoichiometric ratio, followed by drying and sintering to obtain M-LiFePO4 material. It should be noted that the Fe2O3-C / MO composite material refers to a Fe2O3 plate-like precursor with a carbon layer (C) and metal oxide particles (MO) deposited on its surface. The symbol "-" indicates that Fe2O3 and C / MO have a layered structure, with the carbon layer (C) and metal oxide particles (MO) directly deposited on the surface of the Fe2O3 plate-like precursor. The symbol " / " indicates that the carbon layer (C) and metal oxide particles (MO) are arranged side-by-side, with some areas of the Fe2O3 plate-like precursor having a carbon layer (C), some having metal oxide particles (MO), or some having both simultaneously deposited. In the product M-LiFePO4, the symbol "-" indicates that metal ions M are doped into LiFePO4; the doping location is not limited, as long as doping is achieved.

[0044] In this disclosure, a porous Fe2O3 sheet precursor is used as the matrix, and an organometallic compound is used as the deposition raw material. The organometallic compound contains both carbon and doped metal, so it can be used as a carbon source and a doped metal source. By depositing a carbon layer and metal oxide particles on the surface of the porous Fe2O3 sheet precursor, a Fe2O3-C / MO composite material is obtained. After mixing the Fe2O3-C / MO composite material with a lithium source and a phosphorus source, it is calcined at high temperature to obtain a lithium iron phosphate sheet with a two-dimensional porous structure and metal ion doping, thereby achieving the purpose of increasing the electronic conductivity of the material, promoting the rapid diffusion of lithium ions, and improving the electrochemical performance of the material.

[0045] Specifically, please refer to Figure 1 The method for preparing metal ion-doped lithium iron phosphate materials disclosed herein includes the following steps:

[0046] Preparation of S1 porous Fe2O3 sheet precursor.

[0047] Ferric hydroxide is prepared by heating a mixture of ferric salt, urea, and water under reflux; the ferric hydroxide is then calcined to obtain the final product.

[0048] The ferric salt is at least one of ferric nitrate, ferric chloride, and ferric sulfate. The molar ratio of the ferric salt to urea is 1:(10-15). The reflux reaction is carried out at a temperature of 90℃-110℃ for 12-16 hours, followed by standing at 85℃-95℃ for 5-8 hours. After the reaction is complete, the ferric hydroxide carbonate is collected by centrifugation, washed, and dried. The washing and drying process includes washing several times with deionized water, then several times with anhydrous ethanol, and finally drying in a vacuum oven at 70℃-90℃.

[0049] In this disclosure, ferric hydroxide carbonate is prepared by heating and reflux reaction. During the subsequent calcination process, the ferric hydroxide carbonate undergoes high-temperature pyrolysis to generate gas, thereby forming a porous Fe2O3 plate-like precursor.

[0050] In some typical embodiments, the molar ratio of ferric salt to urea can be, for example, any one or a range between 1:10, 1:11, 1:12, 1:13, 1:14, and 1:15. The temperature for reflux reaction can be, for example, any one or a range between 90°C, 95°C, 100°C, 105°C, and 110°C. The reflux time can be, for example, any one or a range between 12h, 13h, 14h, 15h, and 16h. The settling temperature can be, for example, any one or a range between 85°C, 86°C, 87°C, 88°C, 89°C, 90°C, 91°C, 92°C, 93°C, 94°C, and 95°C. The settling time can be, for example, any one or a range between 5h, 6h, 7h, and 8h. The drying temperature of the vacuum oven can be, for example, any one of 70°C, 75°C, 80°C, 85°C, 90°C, or a range between any two.

[0051] Calcination involves placing ferric hydroxide carbonate in a muffle furnace, heating it to 500°C to 600°C at a heating rate of 3°C / min to 10°C / min, and calcining it in air for 1 to 2 hours to pyrolyze and release CO2 and H2O from the products.

[0052] In some typical embodiments, the heating rate can be, for example, any one or a range of any two of 3°C / min, 4°C / min, 5°C / min, 6°C / min, 7°C / min, 8°C / min, 9°C / min, and 10°C / min. The calcination temperature can be, for example, any one or a range of any two of 500°C, 530°C, 550°C, 580°C, and 600°C. The calcination time can be, for example, any one or a range of any two of 1h, 1.5h, and 2h.

[0053] In this disclosure, a porous Fe2O3 sheet precursor is prepared by heating and reflux and calcination. The porous Fe2O3 sheet precursor has a two-dimensional porous structure and a larger specific surface area, which is beneficial for subsequent contact with organometallic compounds.

[0054] Preparation of S2, Fe2O3-C / MO composite materials.

[0055] Using an organometallic compound as the deposition feedstock, a carbon layer and metal oxide particles are deposited on the surface of a porous Fe₂O₃ sheet precursor to obtain an Fe₂O₃-C / MO composite material. The molar ratio of iron to the organometallic compound in the porous Fe₂O₃ sheet precursor is 1:(0.03–0.1). In some typical embodiments, the molar ratio of iron to the organometallic compound in the porous Fe₂O₃ sheet precursor can be, for example, any one of 1:0.03, 1:0.05, 1:0.08, 1:0.1, or a range between any two.

[0056] The organometallic compounds include at least one of bis(cyclopentadiene)cobalt, cyclododecanetriene nickel, and cyclopentadiene tricarbonylmanganese. This disclosure selects the aforementioned specific organometallic compounds as deposition raw materials. Because they simultaneously contain carbon and doped metals, they can simultaneously deposit carbon layers and metal oxide particles on the surface of the porous Fe2O3 sheet-like precursor. Both the carbon layer and the metal oxide particles can improve the electronic conductivity of the material. Furthermore, the metal ion source can induce internal lattice defects in lithium iron phosphate, reducing the obstacles encountered by lithium ions during insertion and extraction in the layered crystal structure, facilitating the stable diffusion of lithium ions into the material's lattice, and thus greatly improving the rate performance of lithium iron phosphate materials.

[0057] The deposition includes chemical vapor deposition (CVD), with a reaction temperature of 450°C–550°C and a reaction time of 1–2 hours, performed under a protective atmosphere. The aforementioned organometallic compounds can decompose into volatile substances at 450°C–550°C, thereby generating chemical and transport reactions on a solid porous Fe₂O₃ sheet precursor via CVD, producing solid deposits, including carbon layers and metal oxide particles. This method is simple to operate and can uniformly distribute carbon layers and metal oxide particles on the porous Fe₂O₃ sheet precursor. In some typical embodiments, the CVD reaction temperature can be any or a range between 450°C, 460°C, 470°C, 480°C, 490°C, 500°C, 510°C, 520°C, 530°C, 540°C, and 550°C.

[0058] Preparation of S3 and M-LiFePO4 materials.

[0059] Fe2O3-C / MO composite material, lithium source, and phosphorus source were mixed at a molar ratio of 1:(0.98~1.03):1. The Fe2O3-C / MO composite material, lithium source, and phosphorus source were then dispersed in anhydrous ethanol and ball-milled for 2h~5h at a speed of 2000rpm~4000rpm. After drying, pre-calcination at 400℃~550℃ for 2h~5h and sintering at 650℃~750℃ for 6h~10h, M-LiFePO4 material was obtained. The lithium source included at least one of lithium carbonate, lithium hydroxide, and lithium acetate. The phosphorus source included at least one of ammonium dihydrogen phosphate, ammonium hydrogen phosphate, and sodium hydrogen phosphate.

[0060] In some typical embodiments, the molar ratio of the Fe2O3-C / MO composite material, the lithium source, and the phosphorus source can be, for example, any one or a range between any two of 1:0.98:1, 1:0.99:1, 1:1:1, 1:1.01:1, 1:1.02:1, and 1:1.03:1. The ball milling mixing time can be, for example, any one or a range between any two of 2h, 3h, 4h, and 5h. The ball milling speed can be, for example, any one or a range between any two of 2000rpm, 2500rpm, 3000rpm, 3500rpm, and 4000rpm. The pre-calcination temperature can be, for example, any one or a range between any two of 400℃, 430℃, 450℃, 500℃, 520℃, and 550℃. The pre-calcination time can be, for example, any one or a range between any two of 2h, 3h, 4h, and 5h. The sintering temperature can be, for example, any one of 650℃, 680℃, 700℃, 720℃, 740℃, 750℃, or a range between any two. The sintering time can be, for example, any one of 6h, 7h, 8h, 9h, 10h, or a range between any two.

[0061] In this disclosure, M-LiFePO4 material is prepared by directly mixing and grinding Fe2O3-C / MO composite material, lithium source, and phosphorus source, followed by drying and calcination. The Fe2O3-C / MO composite material contains iron, carbon, and metal dopants. Fe2O3 is used to provide a porous sheet structure. The M-LiFePO4 material inherits the two-dimensional sheet-like porous morphology of the precursor material. The high-temperature pyrolysis of ferric hydroxide carbonate releases water vapor and carbon dioxide, which can generate a porous structure in the two-dimensional Fe2O3 sheets. Furthermore, during the high-temperature calcination process under a protective atmosphere, Fe2O3 and carbon atoms in the carbon layer deposited on its surface undergo a redox reaction, consuming carbon atoms and thus achieving the purpose of etching the carbon layer, which can also generate a porous structure to a certain extent. Therefore, these two factors synergistically create a porous structure, increasing the surface area. Compared to bulk lithium iron phosphate materials with irregular structures, this two-dimensional structure has a larger specific surface area and abundant electrochemical reactive sites. This is beneficial for sufficient contact between the electrode and the electrolyte and for accelerating the lithium-ion insertion / extraction rate. Furthermore, the presence of the porous structure provides ion channels for the diffusion of electrolyte ions in the vertical direction of the two-dimensional nanosheets, significantly reducing charge transport resistance and shortening the transport path and diffusion time of lithium ions and electrons. This is beneficial for improving the fast charge / discharge capability of the cathode material under high specific current. In addition, the metal ion source can induce internal lattice defects in lithium iron phosphate, reducing the obstacles encountered by lithium ions during insertion / extraction in the layered crystal structure. This facilitates the stable diffusion of lithium ions into the material's lattice interior, thereby greatly improving the rate performance of lithium iron phosphate materials.

[0062] The aforementioned metal ion-doped lithium iron phosphate materials can be widely used as cathode materials in the preparation of lithium-ion batteries.

[0063] Specifically, this disclosure also provides a lithium-ion battery comprising the aforementioned metal ion-doped lithium iron phosphate material. The prepared lithium-ion battery can be widely used in the fabrication of smart grids or portable electronic devices.

[0064] The features and performance of this disclosure will be further described in detail below with reference to embodiments.

[0065] Example 1:

[0066] A method for preparing a metal ion-doped lithium iron phosphate material and its application, comprising:

[0067] (1) Dissolve 0.02 mol of ferric nitrate and 0.3 mol of urea in 100 mL of deionized water. After stirring evenly, transfer the mixture to a reflux reactor and heat it. Reflux at 100 °C for 12 h, then let it stand at 90 °C for 5 h. After the reaction is complete, centrifuge to collect the ferric hydroxide product. Wash it several times with deionized water and anhydrous ethanol, and dry it in a vacuum oven at 80 °C. Then, place the ferric hydroxide product in a muffle furnace and calcine it at 500 °C for 2 h in air atmosphere to obtain porous Fe2O3 sheet material, which is then ground for later use.

[0068] (2) The porous Fe2O3 sheet precursor powder from step (1) was placed in the reaction chamber of a chemical vapor deposition system. 0.001 mol of bis(cyclopentadiene)cobalt was used as the deposition raw material. In a nitrogen atmosphere (N2: 99%; O2: 0.2%~1%), a carbon thin layer and CoO were deposited on the surface of the Fe2O3 sheet at 500°C for 1.5 h to obtain the Fe2O3-C / CoO composite material. (The molar ratio of iron to organometallic compound was 1:0.05).

[0069] (3) Fe2O3-C / CoO, lithium carbonate, and ammonium dihydrogen phosphate were dispersed in anhydrous ethanol at a molar ratio of 1:1.02:1 for the iron source composite material, lithium source, and phosphorus source. The mixture was ball-milled for 3 hours at 3000 rpm until homogeneous, and then spray-dried to obtain precursor powder. Subsequently, the precursor powder was heated to 400℃ for 3 hours at a heating rate of 5℃ / min under a high-purity argon atmosphere, and then calcined at 700℃ for 8 hours to obtain cobalt ion-doped Co-LiFePO4 cathode material.

[0070] Please refer to the scanning electron microscope image of the Co-LiFePO4 cathode material provided in this embodiment. Figure 2 Please refer to the XRD pattern. Figure 3 .from Figure 2 It can be seen that it has a two-dimensional sheet-like morphology and a porous structure, and exhibits good uniformity and is not prone to aggregation. From Figure 3 It can be seen that the XRD pattern of Example 1 has the same characteristic peaks as the LiFePO4 standard card, and there are no other impurity diffraction peaks, indicating that cobalt metal ions have entered the interior of the lithium iron phosphate crystal structure and formed a continuous solid solution, without affecting the crystal structure of lithium iron phosphate.

[0071] Example 2:

[0072] A method for preparing a metal ion-doped lithium iron phosphate material and its application, comprising:

[0073] (1) Dissolve 0.02 mol of ferric nitrate and 0.3 mol of urea in 100 mL of deionized water. After stirring evenly, transfer the mixture to a reflux reactor and heat it. Reflux at 100 °C for 14 h, then let it stand at 90 °C for 7 h. After the reaction is complete, centrifuge to collect the ferric hydroxide product. Wash it several times with deionized water and anhydrous ethanol, and dry it in a vacuum oven at 80 °C. Then, place the ferric hydroxide product in a muffle furnace and calcine it at 550 °C for 2 h in air atmosphere to obtain a porous Fe2O3 sheet precursor, which is then ground for later use.

[0074] (2) Same as step (2) in Example 1, except that the amount of bis(cyclopentadiene)cobalt is changed from 0.001 mol to 0.0014 mol. (The molar ratio of iron to organometallic compound is 1:0.07).

[0075] (3) is the same as step (3) in Example 1.

[0076] Example 3:

[0077] A method for preparing a metal ion-doped lithium iron phosphate material and its application, comprising:

[0078] (1) Dissolve 0.03 mol of ferric nitrate and 0.45 mol of urea in 100 mL of deionized water. After stirring evenly, transfer the mixture to a reflux reactor and heat it. Reflux at 100 °C for 14 h, then let it stand at 90 °C for 7 h. After the reaction is complete, centrifuge to collect the ferric hydroxide product. Wash it several times with deionized water and anhydrous ethanol, and dry it in a vacuum oven at 80 °C. Then, place the ferric hydroxide product in a muffle furnace and calcine it at 550 °C for 2 h in air atmosphere to obtain a porous Fe2O3 sheet precursor, which is then ground for later use.

[0079] (2) Same as step (2) in Example 1, except that the amount of bis(cyclopentadiene)cobalt is changed from 0.001 mol to 0.0015 mol. (The molar ratio of iron to organometallic compound is 1:0.05).

[0080] (3) is the same as step (3) in Example 1.

[0081] Example 4:

[0082] A method for preparing a metal ion-doped lithium iron phosphate material and its application, comprising:

[0083] (1) Dissolve 0.03 mol of ferric nitrate and 0.45 mol of urea in 100 mL of deionized water. After stirring evenly, transfer the mixture to a reflux reactor and heat it. Reflux at 100 °C for 16 h, then let it stand at 90 °C for 8 h. After the reaction is complete, centrifuge to collect the ferric hydroxide product. Wash it several times with deionized water and anhydrous ethanol, and dry it in a vacuum oven at 80 °C. Then, place the ferric hydroxide product in a muffle furnace and calcine it at 600 °C for 2 h in air atmosphere to obtain a porous Fe2O3 sheet precursor, which is then ground for later use.

[0084] (2) Same as step (2) in Example 3, except that the amount of bis(cyclopentadiene)cobalt is changed from 0.0015 mol to 0.0024 mol. (The molar ratio of iron to organometallic compound is 1:0.08).

[0085] (3) is the same as step (3) in Example 1.

[0086] Example 5:

[0087] A method for preparing a metal ion-doped lithium iron phosphate material and its application, including:

[0088] (1) is the same as step (1) in Example 1, except that the molar amount of ferric nitrate is 0.01 mol and the molar amount of urea is 0.15 mol.

[0089] (2) Same as step (2) in Example 1, except that the amount of bis(cyclopentadiene)cobalt is changed from 0.001 mol to 0.0006 mol. (The molar ratio of iron to organometallic compound is 1:0.03).

[0090] (3) Fe2O3-C / CoO, lithium carbonate, and ammonium dihydrogen phosphate were dispersed in anhydrous ethanol at a molar ratio of 1:0.98:1 for the iron source composite material, lithium source, and phosphorus source. The mixture was ball-milled for 2 hours until homogeneous at a speed of 4000 rpm, and then spray-dried to obtain precursor powder. Subsequently, the precursor powder was heated to 500℃ for 4 hours at a heating rate of 5℃ / min under a high-purity argon atmosphere, and then calcined at 650℃ for 10 hours to obtain cobalt ion-doped Co-LiFePO4 cathode material.

[0091] Example 6:

[0092] A method for preparing a metal ion-doped lithium iron phosphate material and its application, including:

[0093] (1) The same as step (1) in Example 1, except that the molar amount of ferric nitrate is 0.04 mol and the molar amount of urea is 0.6 mol.

[0094] (2) Same as step (2) in Example 1, except that the amount of bis(cyclopentadiene)cobalt is changed from 0.001 mol to 0.004 mol. (The molar ratio of iron to organometallic compound is 1:0.1).

[0095] (3) Fe2O3-C / CoO, lithium carbonate, and ammonium dihydrogen phosphate were dispersed in anhydrous ethanol at a molar ratio of 1:1:1 for the iron source composite material, lithium source, and phosphorus source. The mixture was ball-milled for 5 hours until homogeneous at 2000 rpm, and then spray-dried to obtain precursor powder. Subsequently, the precursor powder was heated to 550°C for 2 hours at a heating rate of 5°C / min under a high-purity argon atmosphere, and then calcined at 750°C for 6 hours to obtain cobalt ion-doped Co-LiFePO4 cathode material.

[0096] Comparative Example 1 (Compared with Example 1, no precursor material was prepared; lithium iron phosphate material without metal ion doping was synthesized by high-temperature solid-state method)

[0097] According to the stoichiometric ratio of ferric oxide, lithium, phosphorus, and carbon sources of 1:1.02:1:0.1, 0.02 mol of ferric oxide particles, 0.0204 mol of lithium carbonate, 0.02 mol of ammonium dihydrogen phosphate, and 0.002 mol of glucose were dispersed in 50 mL of anhydrous ethanol and ball-milled for 3 h at 3000 rpm until homogeneous. The mixture was then spray-dried to obtain precursor powder. Subsequently, the precursor powder was heated to 400 °C for 1.5 h at a heating rate of 8 °C / min under a high-purity argon atmosphere, and then calcined at 700 °C for 8 h to obtain LiFePO4 cathode material.

[0098] Comparative Example 2 (Compared with Example 1, no precursor material was prepared; cobalt ion-doped lithium iron phosphate material was synthesized by high-temperature solid-state method)

[0099] Following a stoichiometric ratio of ferric oxide, metal ion, lithium, phosphorus, and carbon sources of 1:0.05:1.02:1:0.1, 0.02 mol of ferric oxide particles, 0.001 mol of bis(cyclopentadiene)cobalt, 0.0204 mol of lithium carbonate, 0.02 mol of ammonium dihydrogen phosphate, and 0.002 mol of glucose were dispersed in 50 mL of anhydrous ethanol and ball-milled for 3 h at 3000 rpm until homogeneous. The mixture was then spray-dried to obtain precursor powder. Subsequently, the precursor powder was heated to 400 °C for 1.5 h at a heating rate of 8 °C / min under a high-purity argon atmosphere, followed by calcination at 700 °C for 8 h to obtain Co. 2+ Doped Co-LiFePO4 cathode material.

[0100] Comparative Example 3 (Compared with Example 1, a two-dimensional Fe2O3 sheet precursor was prepared, and lithium iron phosphate material without metal ion doping was synthesized by high-temperature solid-state method)

[0101] (1) is the same as step (1) in Example 1.

[0102] (2) Fe2O3 flakes, lithium carbonate, ammonium dihydrogen phosphate, and glucose were dispersed in 50 mL of anhydrous ethanol according to a stoichiometric ratio of 1:1.02:1:0.1 for the iron, lithium, phosphorus, and carbon sources. The mixture was ball-milled for 3 h until homogeneous at 3000 rpm, and then spray-dried to obtain precursor powder. Subsequently, the precursor powder was heated to 400 °C for 1.5 h at a heating rate of 8 °C / min under a high-purity argon atmosphere, and then calcined at 700 °C for 8 h to obtain LiFePO4 cathode material.

[0103] Comparative Example 4:

[0104] This comparative example is basically the same as Example 1, except that the amount of bis(cyclopentadiene)cobalt in step (2) is changed from 0.001 mol to 0.004 mol. (The molar ratio of iron to organometallic compound is 1:0.2).

[0105] Experimental example:

[0106] The lithium iron phosphate cathode material obtained above was used to formulate coin cells for lithium-ion battery electrochemical performance testing (charge and discharge voltage controlled between 2.5-4.5V). The results are shown in the table below:

[0107]

[0108] As can be seen from the table above, the electrochemical performance of the lithium iron phosphate products prepared in Examples 1-6 is significantly better than that of the comparative examples, especially Example 4. Specifically, the random lithium iron phosphate bulk material prepared in Comparative Example 1 has significantly lower discharge specific capacity and initial charge-discharge efficiency than Examples 1-6 and other comparative examples. Although the cobalt-doped random lithium iron phosphate bulk material prepared in Comparative Example 2 has slightly improved discharge specific capacity and initial charge-discharge efficiency compared to Comparative Example 1, it is still significantly worse than Examples 1-6. Although the lithium iron phosphate sheet material without metal ion doping prepared in Comparative Example 3 has slightly improved discharge specific capacity and initial charge-discharge efficiency compared to Comparative Example 1, it is still significantly worse than Examples 1-6. In Comparative Example 4, the molar ratio of iron to organometallic compound in the porous Fe2O3 sheet precursor is outside the range specified in this application. Excessive organometallic compound content leads to excessive doped metal content, which hinders lithium ion insertion / extraction and thus affects the electrical performance of the electrode material. The lithium iron phosphate prepared in Examples 1-6 of this disclosure has a two-dimensional porous sheet structure and is doped with metal ions. The material with this structure has a large specific surface area and high conductivity. The contact area between the electrolyte and the positive electrode material is large, the diffusion path of lithium ions is shortened and the insertion and extraction speed is fast, thus improving the rate performance of the lithium battery.

[0109] In summary, the metal-doped lithium iron phosphate material disclosed herein possesses a two-dimensional sheet-like porous morphology and is doped with metal ions. Compared to irregular bulk lithium iron phosphate materials, this two-dimensional structure exhibits a larger specific surface area and abundant electrochemical reactive sites, which facilitates sufficient contact between the electrode and the electrolyte and accelerates the lithium-ion insertion / extraction rate. Furthermore, the presence of the porous structure provides ion channels for the diffusion of electrolyte ions in the vertical direction of the two-dimensional nanosheets, significantly reducing charge transport resistance and shortening the transport path and diffusion time of lithium ions and electrons. This is beneficial for improving the fast charge-discharge capability of the cathode material under high specific current. The metal ions doped on the lithium iron phosphate material can induce internal lattice defects, which is beneficial for improving the rate performance of the lithium iron phosphate material. Furthermore, the method for preparing metal-doped lithium iron phosphate materials disclosed herein uses Fe2O3 sheets as a precursor material and organometallic compounds as both a carbon source and a source of doped metal ions. The resulting metal-doped lithium iron phosphate material inherits the two-dimensional porous structure of the precursor material, and both the carbon source and the metal ion source can improve the electronic conductivity of the material. Moreover, the metal ion source introduced through the organometallic compound not only introduces internal lattice defects into lithium iron phosphate, reducing the obstacles encountered by lithium ions during insertion and extraction in the layered crystal structure, but also facilitates the stable diffusion of lithium ions into the material's lattice, thereby greatly improving the rate performance of the lithium iron phosphate material. The lithium iron phosphate sheets synthesized in this disclosure exhibit good uniformity and are not prone to agglomeration; the process is simple, easy to operate, and has low energy consumption, showing promising prospects for industrial application.

[0110] The optional embodiments of this disclosure have been described in detail above; however, this disclosure is not limited thereto. Within the scope of the technical concept of this disclosure, various simple modifications can be made to the technical solutions of this disclosure, including combining the various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in this disclosure and are all within the protection scope of this disclosure.

[0111] Industrial applicability

[0112] The metal-doped lithium iron phosphate material disclosed herein possesses a two-dimensional sheet-like porous morphology and is doped with metal ions. Compared to irregular bulk lithium iron phosphate materials, this two-dimensional structure exhibits a larger specific surface area and abundant electrochemical reactive sites, which facilitates sufficient contact between the electrode and the electrolyte and accelerates the lithium-ion insertion / extraction rate. Furthermore, the presence of the porous structure provides ion channels for the diffusion of electrolyte ions in the vertical direction of the two-dimensional nanosheets, significantly reducing charge transport resistance and shortening the transport path and diffusion time of lithium ions and electrons. This is beneficial for improving the fast charge / discharge capability of the cathode material under high specific current. The metal ions doped on the lithium iron phosphate material can induce internal lattice defects, which is beneficial for improving the rate performance of the lithium iron phosphate material. Furthermore, the method for preparing metal-doped lithium iron phosphate materials disclosed herein uses Fe2O3 sheets as a precursor material and organometallic compounds as both a carbon source and a source of doped metal ions. The resulting metal-doped lithium iron phosphate material inherits the two-dimensional porous structure of the precursor material, and both the carbon source and the metal ion source can improve the electronic conductivity of the material. Moreover, the metal ion source introduced through the organometallic compound not only introduces internal lattice defects into lithium iron phosphate, reducing the obstacles encountered by lithium ions during insertion and extraction in the layered crystal structure, but also facilitates the stable diffusion of lithium ions into the material's lattice, thereby greatly improving the rate performance of the lithium iron phosphate material. The lithium iron phosphate sheets synthesized in this disclosure exhibit good uniformity and are not prone to agglomeration; the process is simple, easy to operate, and has low energy consumption, showing promising prospects for industrial application.

Claims

1. A method for preparing a metal ion-doped lithium iron phosphate material, characterized by, It comprises: The Fe2O3-C / MO composite material is obtained by depositing carbon layer and metal oxide particles on the surface of porous Fe2O3 flaky precursor by using organic metal compound as deposition raw material, wherein M is one of Co 2+ , Ni 2+ , Mn 2+ ​ The Fe2O3-C / MO composite material, a lithium source and a phosphorus source are mixed according to a stoichiometric ratio, and then dried and sintered to obtain the M-LiFePO4 material. The molar ratio of iron elements in the porous Fe2O3 flaky precursor to the organic metal compound is 1:(0.03-0.1); the molar ratio of the Fe2O3-C / MO composite material, the lithium source and the phosphorus source is 1:(0.98-1.03):

1.

2. The method for preparing metal ion-doped lithium iron phosphate material according to claim 1, characterized in that, The organic metal compound includes at least one of bis(cyclopentadiene) cobalt, cyclododecatriene nickel and cyclopentadiene manganese tricarbonyl.

3. The method of producing a metal ion-doped lithium iron phosphate material according to any one of claims 1 to 2, characterized in that, The deposition includes chemical vapor deposition.

4. The method for preparing metal ion-doped lithium iron phosphate material according to claim 3, characterized in that, The reaction temperature of the chemical vapor deposition is 450-550 DEG C, and the reaction time is 1-2 h.

5. The method of claim 3, wherein the metal ion-doped lithium iron phosphate material is prepared by a process comprising: mixing a lithium source, an iron source, and a phosphate source to form a mixture; and heating the mixture to a temperature of 600 °C to 800 °C in the presence of a metal ion dopant. The chemical vapor deposition is performed under a protective atmosphere.

6. The method of claim 1, wherein the metal-ion doped lithium iron phosphate material is prepared by a process comprising: mixing a lithium source, an iron source, a phosphate source, and a metal-ion source to form a mixture; and heating the mixture to form the metal-ion doped lithium iron phosphate material. The preparation method of the porous Fe2O3 flaky precursor includes: preparing iron hydrogencarbonate by heating and refluxing a mixed solution of a ferric salt, urea and water; and calcining the iron hydrogencarbonate to obtain the product.

7. The method of claim 6, wherein the metal ion-doped lithium iron phosphate material is prepared by a process comprising: mixing a lithium source, an iron source, and a phosphate source to form a mixture; and heating the mixture to a temperature of 600 °C to 800 °C in the presence of a dopant metal source. The molar ratio of the ferric salt to the urea is 1:(10-15).

8. The method of claim 6, wherein the metal ion-doped lithium iron phosphate material is prepared by a process comprising: mixing a lithium source, an iron source, and a phosphate source to form a mixture; and heating the mixture to a temperature of 600 °C to 800 °C in the presence of a dopant metal source. The heating and refluxing reaction is performed at a temperature of 90-110 DEG C, a refluxing time of 12-16 h, and a standing time of 5-8 h at 85-95 DEG C; after the reaction is completed, the iron hydrogencarbonate is collected by centrifugation, and then washed and dried.

9. The method of claim 8, wherein the metal ion-doped lithium iron phosphate material is prepared by a process comprising: mixing a lithium source, an iron source, and a phosphate source to form a mixture; and heating the mixture to a temperature of 600 °C to 800 °C in the presence of a metal ion dopant. The washing and drying includes washing several times with deionized water, washing several times with anhydrous ethanol, and then drying in a vacuum oven at 70-90 DEG C.

10. The method for preparing metal ion-doped lithium iron phosphate material according to claim 6, characterized in that, The calcination includes placing the iron hydrogencarbonate in a muffle furnace, heating to 500-600 DEG C, and calcining in an air atmosphere for 1-2 h to pyrolyze CO2 and H2O in the product.

11. The method for preparing metal ion-doped lithium iron phosphate material according to claim 10, characterized in that, The heating rate in the muffle furnace is 3-10 DEG C / min.

12. The method of claim 6, wherein the metal-ion doped lithium iron phosphate material is prepared by a process comprising: mixing a lithium source, an iron source, a phosphate source, and a metal-ion source to form a mixture; and heating the mixture to form the metal-ion doped lithium iron phosphate material. The ferric salt is at least one of ferric nitrate, ferric chloride and ferric sulfate.

13. The method of claim 1, wherein the metal-ion doped lithium iron phosphate material is prepared by a process comprising: mixing a lithium source, an iron source, a phosphate source, and a metal-ion source to form a mixture; and heating the mixture to form the metal-ion doped lithium iron phosphate material. The mixing includes dispersing the Fe2O3-C / MO composite material, the lithium source and the phosphorus source in anhydrous ethanol, and ball-milling and mixing for 2-5 h, wherein the rotation speed of the ball-milling is 2000-4000 rpm.

14. The method of claim 1, wherein the metal-ion doped lithium iron phosphate material is prepared by a process comprising: mixing a lithium source, an iron source, a phosphate source, and a metal-ion source to form a mixture; and heating the mixture to form the metal-ion doped lithium iron phosphate material. The sintering further includes pre-sintering before the sintering, wherein the temperature of the pre-sintering is 400-550 DEG C, and the reaction time is 2-5 h.

15. The method for preparing metal ion-doped lithium iron phosphate material according to claim 1, characterized in that, The sintering is performed at a temperature of 650-750 DEG C for a reaction time of 6-10 h.

16. The method of claim 1, wherein the metal-ion doped lithium iron phosphate material is prepared by a process comprising: The lithium source includes at least one of lithium carbonate, lithium hydroxide and lithium acetate. ​ 17. The method for preparing metal ion-doped lithium iron phosphate material according to claim 1, characterized in that, The phosphorus source includes at least one of ammonium dihydrogen phosphate, ammonium hydrogen phosphate and sodium hydrogen phosphate.

18. The method for preparing metal ion-doped lithium iron phosphate material according to claim 1, characterized in that, The M-LiFePO4 material includes flaky lithium iron phosphate and metal ions doped on the flaky lithium iron phosphate, and the flaky lithium iron phosphate has a porous structure.

19. The method of claim 18, wherein the metal-ion doped lithium iron phosphate material is prepared by a process comprising: The thickness of the flaky lithium iron phosphate is 30-60 nm.

20. The method of claim 18, wherein the metal-ion doped lithium iron phosphate material is prepared by a process comprising: The specific surface area of the flaky lithium iron phosphate is 12.5 m 2 / g - 14.7 m 2 / g.

21. The use of the metal ion doped lithium iron phosphate material prepared by the preparation method of the metal ion doped lithium iron phosphate material according to any one of claims 1-20 as a positive electrode material in the preparation of a lithium ion battery.

22. A lithium-ion battery, characterized by, The application relates to a metal ion-doped lithium iron phosphate material, a preparation method of the metal ion-doped lithium iron phosphate material and application of the metal ion-doped lithium iron phosphate material.

23. Use of the lithium ion battery according to claim 22 for the production of a smart grid or a portable electronic device.

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